The princess and her boyfriend Dave Clark joined the newlyweds at the wedding of D.A. Wallach, a musician and business executive who invests in tech companies, and Liz Brinson, who is the founder and editor-in-chief of the fashion and lifestyle blog Swirl Girl Army.

The group traveled to the luxurious Rosewood Mayakoba hotel in Mexico for the nuptials over the weekend.

The foursome “were chatting it up like old friends,” a source tells PEOPLE, as they relaxed at a poolside restaurant for at least an hour on Saturday afternoon.

“Both couples seemed chill, happy and relaxed,” the source adds.

Mila Kunis’s Changing Looks!

Kutcher and Kunis were dressed casually and comfy. Getting into the tropical spirit of the event, the new mom even sported a flower behind her ear.

Just last week, Uber driver David Capellan took a selfie with the foursome, and according to the Instagram caption, he had a “crazy convo” with the group.

The Hollywood couple aren’t the only famous pals for the royal. Earlier this month, she joined Oprah Winfrey and Gayle King aboard a luxury yacht off the coast of Ibiza on the eve of her 27th birthday.

The globe-trotting princess has been making the most of her summer in the sun, as she just started a new job at a private equity firm in N.Y.C., PEOPLE confirms.

Clark, an American-born, London-raised businessman who works for Uber, already resides in the Big Apple. The couple have been dating for more than seven years.

“They seem really happy and very compatible,” the source says of the pair.

• With reporting by ELIZABETH LEONARD

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